In a steam reformer, under high temperatures (e.g., 400-800° C.) and in the presence of a catalyst (e.g., nickel), steam may react with a feed gas (e.g., methane) to generate a reformate (e.g., hydrogen) which may be used as fuel in a hydrogen fuel cell to generate electricity, for example. Because the reforming reaction is endothermic, a heat source is needed to maintain a temperature range at which the reaction can occur. In some examples, the steam reformer may include a burner outside of a reactor which heats the reactor and is fueled by the reformate.